Low cost quick connectors for connecting tubing have been widely used in the automotive industry as well as other non-automotive industries. Typically, they are used to connect fluid lines that have small diameters and low pull-off requirements.
One example of such a quick connector is known as an interference type connector. This type of connector has expandable fingers mounted in a housing that create a mechanical interference on an upset portion or bead formed on the tube to be connected. The tube and upset are inserted into the connector housing past the expandable fingers. The fingers expand to allow the upset to pass and then retract behind the upset retaining the tube in the housing. The retention or pull off force, i.e. the force required to pull the tube out of the housing, is dependent upon the rigidity of the expandable fingers. Stated another way, the retention force of an interference type connector is determined in large part by the resistance to expansion of the fingers. If the fingers expand easily to allow easy insertion of the tube upset, the pull off or retention force will be low. To get higher retention forces, the fingers have to be more rigid, making insertion of the upset more difficult. Additionally, fingers that are more rigid are more difficult to manually expand to remove the tube when removal is desired.
There are many applications which require very high pull-off forces, but low insertion forces. One such application is the connection of the fuel filler neck to the fuel tank of a vehicle. Pull-off forces in excess of 500 pounds are required. Correspondingly, low insertion forces of only about 20 pounds are required. Because of the need for high pull-off forces and low insertion forces, typical quick connectors are unacceptable for connecting fuel filler necks to fuel tanks. They are also unacceptable in other applications requiring high pull-off forces and low insertion forces.